The invention relates to a process for producing packs with an outer wrapper made of film, in particular hinge-lid boxes for cigarettes, a film blank which is folded around the pack having folding tabs which are connected to one another by thermal sealing. The invention also relates to an apparatus for carrying out the process.
Cigarette packs, in particular hinge-lid boxes, are usually constructed such that an outer wrapper made of film encloses the pack. Folding tabs of the outer wrapper, in the region of a narrow side wall and in the region of the end wall and base wall, are connected to one another by thermal sealing.
The quality, namely the outer appearance, of cigarette packs has to meet ever more stringent requirements. This also applies to the outer wrapper of the cigarette pack, in particular hinge-lid box.
Accordingly, the object of the invention is to propose measures, for the treatment of the pack provided with an outer wrapper made of film, which improve the outer appearance of the outer wrapper, in particular in the case of hinge-lid boxes for cigarettes.
In order to achieve this object, the process according to the invention is characterized by the following features:
a) during the production of packs of the hinge-lid type, said packs are transported in a plurality of, in particular two, pack rows arranged one above the other along a straight conveying path for the purpose of sealing laterally directed folds in the region of end wall and base wall,
b) following the sealing of the end walls and base walls, the cyclically transported pack rows are subjected to heat treatment in the vicinity of the conveying path, preferably (only) in the region of the upward-facing front sides of the packs.
According to the process of the invention, the thermal sealing of folding tabs and a shrinkage process are thus carried out in successive steps in the region of a straight conveying path. The shrinkage process is preferably carried out such that heat for shrinking is applied merely to the upwardly directed front sides of the packs or film.
In the case of the apparatus according to the invention, the packs are conveyed, preferably discontinuously, through the sealing station and the following shrinking station in two pack rows located one above the other. In this case, the upwardly directed front sides of the packs are subjected to heat treatment by way of the abutment of heating plates. According to the invention, the top pack row is raised slightly in the region of the shrinking station, with the result that a heating element, in particular a heating plate, can act in the region of the bottom pack row.
A further special feature of the invention is the design of the heating plates such that a very rapid, effective change in the heating temperature is made possible. As a result, the heating and/or shrinking station can be quickly adapted to different operating states of the packaging machine, in particular to different conveying speeds.